1. Field of Invention
The invention relates in general to a method of temperature monitoring, and more particularly to a method of in-line temperature monitoring.
2. Description of Related Art
In semiconductor processes, thermal processes are typically performed in a furnace, of which the temperature is commonly monitored by thermocouples. The way to control the temperature of the furnace is to set an upper and a lower temperature limit through a program. Being monitored by the thermocouples, any abnormal temperature variation or fluctuation can be avoided. If the thermal process is a thermal oxidation process, a variation of the film thickness can be measured as another reference to determine whether the furnace temperature is as specifically required or not.
However, while the film thickness is kept constant since the film does not grow during ion drive-in, anneal and densification processes, the method to monitor the furnace temperature is restricted to the usage of thermocouples only. Should any peripheral hardware of monitoring the furnace temperature malfunction, the temperature cannot be correctly monitored, a great cost is lost due to a large quantity of faulty or failure products.